The research program proposed aims to: (1) Establish the extent to which the procarcinogens can be detected as mutagens in Drosophila; (2) explore the nature and capacity of activating enzymes in the system; (3) investigate whether mutagenic response to procarcinogens can be modified by inducers, inhibitors and cofactors of the MFO-system; (4) isolate and characterize mutagen-sensitive mutants and examine their utility for a better identification of carcinogenic aromatics and polycyclic hydrocarbons; (5) study the relationship between chemical reaction pattern and mutagenic properties of alkylating agents; (6) establish the resolving power (and thus the relative reliability) of different genetic end points used as a measure of mutagenicity at toxic and subtoxic concentrations; and finally (7) evaluate the Drosophila results utilizing data obtained in mammalian systems in which the same chemicals have been used. The results of this work will be critically evaluated to determine the degree of correlation between carcinogenicity (mutagenicity in mammalian systems) and mutagenicity in Drosophila.